Multicontact bimetallic thermal retarder for electric water heaters



y 1947- c. M. OSTERHELD 2,420,189

MULTI-CONTACT BIMETALLIC THERMAL RETARDER FOR ELECTRIC WATER HEATERS Filed Sept. 20, 1944 2 Sheets-Sheet l 3/ 39 INVENTOR.

C2 Am? .05 75mm 0 W m M AT TORNE Y May 6, 1947. c. M. OSTERHELD 2,420,189

MULTI-CONTACT BIMETALLIC THERMAL RETARDER- FOR ELECTRIC WATER HEATERS Filed Sept. 20, 1944 2 Sheets-Sheet 2 7 J25 99 793 /03 63 fig 7 79 a/ f27 6 JJ as 73 f3 7/ n In d- IN V EN TOR. 62 A RX 05' TL'RHH D ATTORNEY Patented May 6, 1947 MULTICONTACT BIMETALLIC THERMAL RETARDER FOR ELECTRIC WATER HEATERS Clark M. Osterheld, Stoughton, Wis., assignor to McGraw Electric Company, Elgin, 111., a corporation of Delaware Application September 20, 1944, Serial No. 554,999

4 Claims. 1

My invention relates to electric heater control d vices, and particularly to thermal retarder heater control switch units.

An object of my invention is to provide a relatively simple and easily manufactured structure to selectively cause either immediate energization of the electric heater of a domestic hot water tank, or energization of the heater with a predetermined time delay period, in accordance with the amount of cold water in the tank at the start of an oil-peak period.

Another object of my invention is to provide a means controlled by the thermal element of a thermal retarder having a heating coil on the thermal element, to control the energization of theheating' coil in accordance with the position oi the thermal element.

In the drawings,

Figure l is a vertical, sectional view of a water tank with a thermal retarder embodying my invention associated therewith, I

Fig. 2 is a diagram of circuits showing the positions of the contacts when the tank is either entirely full of cold water or is at least half full of cold water,

Fig. 3 is a diagram of circuits showing the positions of the contacts when the tank is more than half full of hot water in its upper portion and cold water in its lower portion,

Fig. 4 is a diagram similar to Fig. 3, except the positions of the contacts are shown at the end of a retarding period.

Fig.5 is a modified diagram of circuits embodying a relay which is shown as being deener- "gized,

Fig. 6 is a top plan'view of a thermal retarder nbodying my invention shown in horizontal sec- Fig. 7 is a fragmentary, horizontal, sectional view therethrough taken on the line 'l-| of Fig. 8,

Fig. 8 is a view in side elevation of my improved thermal retarder, with the cover shown in section and when the tank contains cold water at its center portion,

' Fig. 9 is a front elevational view of'the device shhiwn m Fig. 8, with the cover shown in section,

Fig. 10 is a modified diagram of circuits showing a shunting of'the heating coil of the bimetal bar when the tank contains cold water at the center Referring first to Fig. 10f the drawings, I have there shown an ordinary domestic hot water tank it having a lower cold water inlet pipe 23, an

upper hot water outlet pipe 25, a layer 21 of heat.

insulating material therearound, which latter is held in place by an outside casing 29.

I provide also a single electric heater 3|, which may be of the clamp-on type and be located in a tunnel member 33. All of these hereinabove elements are old and well known in the art and constitute no part of my present invention.

I provide a lower thermally-actuable heater control switch, designated generally by the numeral 35, which, while it may be of any kind effective for the given purpose, is shown as comprising a bimetal bar 31, one end of which is fixedly mounted on a contact 39, while the other end thereof is adapted to engage with and be disengaged from a second fixed contact 4|, which two contacts are insulatedly mounted against the outside of the tank so that the bimetal bar 3! will be subject to the temperature of the water in the tank. The design, construction, and adjustment of the thermally-actuable switch 35 is such that it will be in closed position when subject to cold water in the tank and will be in open position when subject to hot'water in the tank. Any desired known method and means may be employed to effect such opening and closing movements under the conditions of cold water having a temperature on the order of to F. and hot water having a temperature on the order of F.

Referring now particularly to Figs. 6, 7, 8, and 9, I have there shown a thermal retarder, which is a modification of that shown and claimed in my copending application, S. N. 554,998 filed September 20, 1944, and assigned to the same assignee as is the present application. The thermal retarder 43 isadapted to be secured against the outer surface of a supporting block 45, whose inner surface is of arcuate shape to fit against the outer arcuate surface of the tank 2|, and the block 45 may be held in fixed position by welding seams 41. The thermal retarder assembly 43 includes a bracket 49, which latter is of substan tially L-shape, the vertically-extending portion thereof being adapted to be secured against the outer surface of block 45 by a plurality of short machine screws 5|. The bracket 49 includes a longitudinally, vertically-extending projection 53 having a short, fiat, vertical surface at its lower portion, against which the lower end of a bimetal bar 55 may be secured as by a pair of machine screws 51. The bimetal bar 55 is relatively long and of the creep-type, that is, its fiexure, with change of temperature, is substantially uniform with the change of temperature.

I provide a horizontally-projecting bracket member 59' secured by a pair of short machine screws 6| against one side of member 53. A block 93, of electric-insulating material, which is of substantially rectangular shape and has a vertical recess 65 in its upper surface, is secured against a front flattened portion 61 of member 59 by screws 69. Members 53 and 63 are provided with aligned openings 1|, 13, and 15 therein for a purpose which will hereinafter appear. A long headed rod 11, having a screw-threaded inner end, is adapted to extend through the aligned openings 1|, 13, and 15, a block 18 of electric-insulating material and of generall tubular shape being located on the central portion of rod 11 and being adapted to be moved thereon by the bimetal bar 55, which is provided with a forked upper end adapted to be engaged between two collars 19 and SI on the inner end of member 18. The inner reduced end portion of member 18 has a coil spring 83 thereon having one end engaging the collar 8|, while the other end engages a collar 85 of electric-insulating material, which collar is adapted to engage a contact bridging member 81 slidably mounted on the inner reduced portion of member 18. The contact bridging member 81 is adapted to engage with and be disengaged from contact members 89 and 9|, which are mounted on the inner vertical surface of block 63.

I provide a second coil spring 93, which is located on the outer end portion of rod 11 between the head of rod or bolt 15 and a collar 95 of electric-insulating material, slidably mounted on rod or bolt 11, the spring 93 being effective to hold the collar 95 away from the head of bolt 11. A second contact bridging member 91 is mounted on collar 95 and is adapted to engage with and be disengaged from a pair of fixed contacts 99 and IN, when the bimetal bar 55 has moved the member 18 as far to the right as is possible and contact bridging member 91 is adapted to engage with a pair of fixed contacts I03 and I05, which are positioned on the inner surface of the outer projection of member 63, when member 18 is moved as far as possible to the right. The contact members 89, 99, and I03 are all electrically connected together, as are also contacts IM and I05. I provide a cover I01, which may be held in proper operative position as by machine screws I09.

The bimetal bar 55 is shown in Fig. 8 of the drawings, in full lines, in the position which it will occupy when subject to cold water in the tank. While I preferably mount the thermal retarder 43 at the mid-height of the tank, I do not desire to be limited thereto, and any statement as to the tank being half full of cold water, so that the bimetal bar 55 is subject to cold water and being half full of hot water, so that bimetal bar 55 is subject to hot water, is to be understood as being subject to slight alterations. The bimetal bar 55 is adapted to be in position II I, shown in broken lines in Fig. 8 of the drawings, when subject to hot water, by which I mean water having a temperature on the order of 150 F. A small heating coil H3 is insulatedly mounted on the outer movable end of bimetal bar 55, and when energized for a period of time, on the order of four to six hours, it will cause ilexure of the bimetal bar 55 in a clockwise direction to the position designated by H in broken lines in Fig. 8 of the drawings. Heating coil H3 is effective to cause a rise of temperature of the outer end o) bimetal bar 55 to a value on the order of 250 F. or more in from four to six hours.

Referring now to Figs. 2, 3, and 4 of the drawings, I have there shown a. diagram of connections, including the lower thermally-actuable heater control switch 35, the thermal retarder 43, and a time-controlled switch 1, shown generally only as including a pair of contact arms H9 and I2I. It is to be understood that the time-controlled switch I I1 is controlled by a continuously operative timer, either of the clock kind or of the electric motor kind, so that the two contact arms will be out of engagement with each other during on-peak periods but will be in engagement with each other during off-peak periods of a twenty-four hour day.

I provide a pair of supply circuit conductors I23 and I 25, of which conductor I23 is connected to contact arm H9. The second contact arm I2| of the time-controlled switch is connected by a. conductor I21 with contacts I03, 99, and 89. Contact 9| is connected by a conductor I29 with one terminal of heating coil H3, the other terminal of which is connected by a conductor I 3| with contact 4| of the lower thermally-actuable switch 35. A conductor I33 connects contact II to one terminal of heater 3 I, the other terminal of which is connected by a conductor I35 with terminal I05 of the thermal retarder switch, which is electrically connected to the other contact IOI. Contact 39 of the lower thermal switch 35 is connected by a conductor I31 with the second supply circuit conductor I25.

Referring first to Fig. 2, I have there shown the contacts in the positions they will occupy when the tank is more than half full of cold water, so that the lower thermal switch 35, as well as the thermal retarder switch 43, will be subject to cold water, with the result that bimetal bar 31 will engage contact 4|, and contact bridging member 91 will engage contacts IN and 99, because of the fact that bimetal bar 55 is flexed in a counter-clockwise direction to the limit of its movement.

If this condition occurs during on-peak periods, that is, say, before 10 p. m., the fact that the time-controlled switch is still open will prevent energization of heater 3|, but when time-controlled switch 1 is closed at the start of an cit-peak period, which we may assume to happen at 10 p. m., then the following energizing circuit is established through heater 3|: from supply circuit conductor I 23 through engaged contact arms 9 and HI, through conductor I21 to contacts I03 and 99, through bridging member 91, through contacts IM and I05. through conductor I35 heater 3| conductor I33, through closed switch 35, and from there through conductor I31 to the second supply circuit conductor I25.

Energization of the heater 3| will continue until the tank 2| is more than half full of hot water at the top portion, so that thermal retarder 43 will be subject to hot water, the bimetal bar 55 being flexed thereby into position III, with the result that the diagram of connections is now as shown in Fig. 3 of the drawings, where contact bridging member 81 is in engagement with contact members 89 and 9|, while contact bridging member 91 is out of engagement with contact members 99 and IN. This new position of bimetal bar 55 will close an energizing circuit through heating coil II3 on bimetal bar 55 through a circuit as follows: from supply circuit conductor I23 through engaged contact arms H9 and HI, conductor I21 through contact member I03 to contact member 39, through bridging member 81 to contact 9|, through conductor I29,

heating coil H3, conductor I3I, through closed switch 35, and from there through conductor I31 to the second supply circuit conductor I25. As has alreadybeen hereinbefore stated, the time necessary to cause heating up of the bimetal bar 55 to a temperature on the order of 250 F., sufflcient to cause flexure thereof to the position shown in Fig. 8, by numeral H5, is on the order of, say, four hours. When this heating up of bimetal bar 55 occurs, the positions of the contacts will be that shown in Fig. 4 of the drawings, with the result that the heater coil 3I is energized through substantially the same circuit as hcreinbefore noted, except that contact bridging member 91 is now in engagement with contacts I03 and I95. Energization of heater 3 I will there fore continue until either all of the water in the tank is hot before the end of the oil-peak period, with resultant opening of the lower thermal heater control switch 35, or in case less than all of the water in the tank is hot at the end of an oil-peak period, heater 3I will be deenergized by opening of the time-controlled switch H1 at the end of an oil-peak period.

This will deenergize not only the heater 3|, but also heating coil H3, with the result that since the thermal retarder 43 is subject to hot water, the parts will move back to the positions shown in Fig. 3 of the drawings, so that the entire system is deenergized.

The device and system embodying my invention, as thus far described, is therefore efiective to cause a predetermined time period of delay in the energization of the heater 3I after the tank is half full of hot water.

Referring now to Fig. 5 of the drawings I have there illustrated another system embodying the thermal retarder and including, in addition to the thermal retarder, the time-controlled switch and the lower thermally-actuable switch, an electromagnetic switch for controlling the energization of the heating coil on the bimetal bar. The electromagnetic switch, designated generally by numeral I 39, comprises a pair of fixed contacts MI and I43, a contact bridging member I45, adapted to be moved into and out 01 engagement with the fixed contacts and connected with a magnetizahle core I41, which is adapted to be energized by a coil I4 9. Contact I43 is connected by a conductor I5I with contact M of the lower thermal switch. Contact I4! is connected by a conductor I53 with one terminal of the heatingcoil H3, while the other terminal of heating coil H3 is connected by a conductor I 55 with contacts 89, 99, and I03. One terminal of coil I49 is connected by a conductor I51 with contact I43, while the other terminal of coil I 49 is connected by a conductor I59 with contact 9I of the thermal relay.

The position of the contacts in Fig. 5 of the drawings is that occupied by them when the thermal retarder is subject to cold water in the tank during an on-peak period. It is evident that at the start of an off-peak period the timecontrolled switch H1 will be closed and thereby provide the hereinbefore described circuit for energizing the heater 3|. When more than half of the water in the tank has been heated, and the bimetal bar 55 has been moved into its intermediate position, designated by numeral II I in Fig. 8 of the drawings and shown schematically in Fig. 3 of the drawings, an energizing circuit for the coil I49 of the electromagnetic switch I 39 'will be closed by engagement of contact bridging member 81 with contacts 39 and SI. This circult is as follows: from supply circuit conductor I23. through engaged contact arms I I9 and I, through conductor I21 to contacts I93 and 89, through bridging member 81 to contact 9|, through conductor I59, coil I49, conductor I51 to contact I43, through conductor I5I to contact 4i, through closed switch 35, and from there through conductor I31 to the second supply circuit conductor I25. This energization of coil I49 will cause quick upward movement of the contact bridging member I 45, with the result of closing an energizing circuit through heating coil H3 substantially as follows: from supply circuit conductor I23 through closed time-controlled switch H1, conductor I21 to contact I03, through con ductor I55, heating coil H3, conductor I53, through engaged contacts MI and I43 with contact bridging member I45, through conductor I5I to contact 4|, through closed switch 35, and from there through conductor I31 to the second supply circuit conductor I25. The heating coil, I I3, thus energized, will cause slow temperature rise of the bimetal bar 55 until, at the end of a predetermined time period, say four hours, the bimetal bar 55 will have flexed in a clockwise direction to position II 5, whereby an energizing circuit through heater 3| is closed, as has already been hereinbefore described and as is shown in Fig. 4 of the drawings. The system shown schematically in Fig. 5 of the drawings is therefore effective to cause energization of heater 3I a predetermined time after at. least one-half the water in the tank is hot, and bimetal bar 55 will have been moved to position III shown in Fig, 8 of the drawings.

Referring now to Fig. 10 or the drawings, I have there illustrated a still further modification of circuit embodying my invention, in which the thermal retarder shown in Figs. 6, 7, 8, and 9 is effective to control the energization of heating coil i I3 in a somewhat different manner.

The terminals of the heating coil H3 are con nected to contacts 89 and SI as by conductors I5! and I63. Contact 9! is connected by a conductor I 65 to one terminal of a fixed current limiting resistance I51, the other terminal of which is connected by a conductor I69 to contact "H of the lower thermally-actuable switch 35. The contact bridging member 91 adapted to engage with and be disengaged from contacts 83 and SI is now positioned on the other side of the contact mem bers 89 and 95, and while I have not shown such a structure specifically, it is thought unnecessary to do so, since the change could very easily be made. When the second contact bridging member 91 is in engagement with contacts 99 and I Ill, then contact bridging member 81 is in engagement with contacts 99 and 9!, thereby sho-rt-circuiting heating coil H3, making it inefifectiv to cause heating of the bimetal bar 55 during the time that heater 3i is energized because of the presence of cold water in the tank, amounting to more than half of a full tank. When the time switch II 1 is closed, as during an ofi-peak period, and assuming that more than half of the tank full of water is hot, the bimetal bar, 55 will have been moved into position III, whereby contact bridging member 91 is moved out of engagement with contacts 99 and Iiil, and contact bridging mem-- ber 81 is moved out of engagement with contacts 89 and 9!, whereby an energizing circuit through heating coil H3 is closed as follows: from supply circuit conductor I23 through engaged contact arms I I9 and I2I, through conductor I21 to contact 89, through conductor IBI, heating coil H3,

conductor I63, contact 9|, conductor I65, resistance lBl, conductor I69, through closed switch 35, and from there through conductor I31 to the second supply circuit conductor I25. This will energize heating coil l i3, with the result that bimetal bar 55 will flex in a clockwise direction after a delay period on the order of four hours or more to cause contact bridging member 91 to move into engagement with contacts 103 and I05, whereby the hereinbefore described energizing circuit through heater 3| is closed. Energization of heater 3! will continue until either substantially all of the water in the tank is hot before opening of the time-controlled switch, in which case thermal switch 35 will open to deenergize the system, or in case less than all of the water in the tank is hot at the end of an oil-peak period, opening of the time-controlled switch II! will deenergize the heater 3!.

It is thus evident that the several systems shown in various views in the drawings, and particularly the thermal retarder shown in Figs. 6, 7, 8, and 9, are efiective to cause a time delay of predetermined length after closure of the time-controlled switch, when the tank is more than half full of hot water, at the end of which delay period energization of the heater is resumed and continued until either all of the water in the tank is hot, if this happens before the end of the offpeak period, or continues until the end of the ofipeak period.

Various other modifications may be made in the systems embodying my invention without departing from the spirit and scope thereof, and all such modifications coming clearly within the scope of the appended claims are to be considered art of my invention.

I claim as my invention:

1. In a thermal retarder switch unit for a hot water storage tank heater to be mounted on a tank intermediate its ends and comprising a heater, a pair of contact bridging members, a bimetal bar operatively connected to said bridging members to actuate the same, three pairs of stationary contact members to be engaged with and disengaged from said bridging members when actuated by said bimetal bar, a heating coil supported by the free end of said bimetal bar, the energization of which is controlled by the first of said contact bridging members and the first pair of cooperating contact members, the second and third pair of contact members being connected in parallel with each other and in series with said heater, said second contact bridging member being moved into engagement with said second pair of contact members when said bimetal bar is subject to cold water in the tank and moved into engagement with said third pair of contact members after a predetermined time period of delay after energization of said heating coil.

2. In a thermal retarder switch unit for a hot water storage tank heater to be mounted on a tank intermediate its ends and comprising a heater, a pair of contact bridging members, a bimetal bar operatively connected to said bridging members to actuate the same, three pairs of stationary contact members to be engaged with and disengaged from said bridging members when actuated by said bimetal bar, a heating coil supported by the free end of said bimetal bar, the energization of which is controlled by the first of said contact bridging members and the first pair of cooperating contact members, the second and third pair of contact members being connected in parallel with each other and in series with said heater, said second contact bridging member being moved into engagement with said second pair of contact members when said bimetal bar is subject to cold water in the tank to energize said heater and said first contact bridging member is moved into engagement with said first pair of contact members to energize said heating coil when said bimetal bar is subject to hot water in the tank and said second contact bridging member is moved into engagement with said third pair of contact members after a predetermined time period of delay after energization of said heating coil.

3. In a thermal retarder switch unit for a hot water storage tank heater to be mounted on a tank intermediate its ends and comprising a heater, a pair of contact bridging members, a bimetal bar operatively connected to said bridging members to actuate the same, three pairs of stationary contact members to be engaged with and disengaged from said bridging members when actuated by said bimetal bar, a heating coil supported by the free end of said bimetal bar, the energization of which is controlled by the first of said contact bridging members and the first pair of cooperating contact members, the second and third pair of contact members being connected in parallel with each other and in series with said heater, said second contact bridging member being moved into engagement with said second pair of contact members when said bimetal bar i subject to cold water in the tank to energize said heater and said first contact bridging member is moved into engagement with said first pair of contact members to energize said heating coil and said second contact member is moved out of engagement with said second pair of contact members when said bimetal bar is subject to hot water in the tank.

4. In a thermal retarder switch unit for a hot water storage tank heater to be mounted on a tank intermediate its ends and comprising a heater, 3. pair of contact bridging members, three pairs of stationary contact members, a bimetal bar operatively connected to said contact bridging members to actuate the same into and out of engagement with said stationary contact members, a heating coil carried by said bimetal bar, an electromagnetic switch controlling the circuit of said heating coil, the coil of said electromagnetic switch being controlled by one of said bridging members and one of said pair of stationary contact members, said bimetal bar holding said second bridging member in engagement with said second pair of contact members when subject to cold water and holding said first bridging member in engagement with said first pair of contact members and said second bridging mem her out of engagement with any contact members when said bimetal bar is subject to hot water in the tank and holding said second bridging member in engagement with said third pair of contact members to energize said heater after a predetermined time delay after energization of said heating coil.

CLARK M. OSTERHELD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date 

